In the treatment of wastewater, such as sewage and the like, it is common to provide a septic tank with an inlet pipe from the source and an outlet pipe for discharge from the tank. Solids in the wastewater settle out to the bottom of the tank while the clarified effluent flows from the tank through the outlet pipe. Effluent leaving the effluent tank may undergo further filtration to remove remaining undissolved particulate materials by passing the effluent through screen filters or similar devices. The effluent may be transported to a second tank for further settling and treatment to remove harmful constituents. Finally, the effluent may be piped into a lateral field where it is passed into a soil bed.
Optionally, wastewater can be further treated before discharge into the environment by utilizing a recirculating system. After leaving the septic tank in a recirculating system, the effluent is passed through a treatment media, which cleans the effluent by filtration and/or bioremediation, and then back to the septic tank, to a separate recirculation tank or back through the filtering system. The filtering system may be a filter bed comprised of stratified layers of sand, gravel or possibly organic matter, wherein the effluent is loaded into the top of the system and trickles through the system to the bottom for collection. The filtering system may include polyurethane or other types of open cell foam having a large surface area through which the effluent trickles and is treated by microorganisms in an aerobic environment.
At some point, the recirculating effluent passes out of the recirculating system and to a receiving body, for example a drain field. A mechanism diverts the filtered effluent to the receiving body. One mechanism utilized is to simply divert a portion of the total effluent returned from filtration through the filtering system. However, this potentially results in a percentage of the wastewater passing through the filtration system only once before discharge. Further, if a sufficient quantity of wastewater is not constantly added to the system to offset the constant flow out of the system, the water level may drop enough that the pumps are damaged by running dry and/or the filtering system dries out, killing essential organisms necessary for treatment of the effluent. Also, if the volume increases faster than the amount of effluent removed from the system, it can overflow.
Alternatively, a means of detecting either effluent flow or effluent level in the septic tank or recirculation tank is used to direct the effluent either out to a drain field or back into the treatment media. Thus, if effluent volume within the system is detected as reaching a critical maximum or minimum, a device seals one of the passages, either to the drain field or back into the system, and diverts the flow where it is needed. The sealing device may be a caged ball float that acts to seal a pipe when the water level within a tank rises enough to force the float over the pipe opening. This system has the disadvantage of diverting all or none of the effluent volume. Thus, it is possible that improperly filtered effluent can be discharged from the system if the level rises too high and all the effluent is diverted directly to the drain field. Further, the ball float makes an inferior valve in that it may not seal properly and is difficult to adjust so that it seals at the proper fluid level.
It would be advantageous to have a recirculation device for use in septic systems employing treatment media that sense the level of effluent and divert only a portion of the effluent when required. Such a system would have the advantage of ensuring adequate filtration of all effluent before discharge from the system. Such a system would be most beneficial for treatment systems where the flow volume varied greatly over time.